arm64 has a feature called Top Byte Ignore, which allows to embed pointer tags into the top byte of each pointer. Userspace programs (such as HWASan, a memory debugging tool [1]) might use this feature and pass tagged user pointers to the kernel through syscalls or other interfaces.
This patch makes a few of the kernel interfaces accept tagged user pointers. The kernel is already able to handle user faults with tagged pointers and has the untagged_addr macro, which this patchset reuses.
Thanks!
[1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html
Changes in v6: - Added annotations for user pointer casts found by sparse. - Rebased onto 050cdc6c (4.19-rc1+).
Changes in v5: - Added 3 new patches that add untagging to places found with static analysis. - Rebased onto 44c929e1 (4.18-rc8).
Changes in v4: - Added a selftest for checking that passing tagged pointers to the kernel succeeds. - Rebased onto 81e97f013 (4.18-rc1+).
Changes in v3: - Rebased onto e5c51f30 (4.17-rc6+). - Added linux-arch@ to the list of recipients.
Changes in v2: - Rebased onto 2d618bdf (4.17-rc3+). - Removed excessive untagging in gup.c. - Removed untagging pointers returned from __uaccess_mask_ptr.
Changes in v1: - Rebased onto 4.17-rc1.
Changes in RFC v2: - Added "#ifndef untagged_addr..." fallback in linux/uaccess.h instead of defining it for each arch individually. - Updated Documentation/arm64/tagged-pointers.txt. - Dropped "mm, arm64: untag user addresses in memory syscalls". - Rebased onto 3eb2ce82 (4.16-rc7).
Andrey Konovalov (11): arm64: add type casts to untagged_addr macro uaccess: add untagged_addr definition for other arches arm64: untag user addresses in access_ok and __uaccess_mask_ptr mm, arm64: untag user addresses in mm/gup.c lib, arm64: untag addrs passed to strncpy_from_user and strnlen_user arm64: untag user address in __do_user_fault fs, arm64: untag user address in copy_mount_options usb, arm64: untag user addresses in devio arm64: update Documentation/arm64/tagged-pointers.txt selftests, arm64: add a selftest for passing tagged pointers to kernel arm64: annotate user pointers casts detected by sparse
Documentation/arm64/tagged-pointers.txt | 5 +-- arch/arm64/include/asm/compat.h | 2 +- arch/arm64/include/asm/uaccess.h | 16 ++++++---- arch/arm64/kernel/perf_callchain.c | 4 +-- arch/arm64/kernel/signal.c | 16 +++++----- arch/arm64/kernel/signal32.c | 6 ++-- arch/arm64/mm/fault.c | 4 +-- block/compat_ioctl.c | 15 +++++---- drivers/ata/libata-scsi.c | 2 +- drivers/block/loop.c | 2 +- drivers/gpio/gpiolib.c | 8 +++-- drivers/input/evdev.c | 2 +- drivers/media/dvb-core/dvb_frontend.c | 3 +- drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 9 +++--- drivers/mmc/core/block.c | 6 ++-- drivers/mtd/mtdchar.c | 2 +- drivers/net/tap.c | 2 +- drivers/net/tun.c | 2 +- drivers/spi/spidev.c | 6 ++-- drivers/tty/tty_ioctl.c | 3 +- drivers/tty/vt/vt_ioctl.c | 5 +-- drivers/usb/core/devio.c | 10 ++++-- drivers/vfio/vfio.c | 6 ++-- drivers/video/fbdev/core/fbmem.c | 4 +-- drivers/xen/gntdev.c | 6 ++-- drivers/xen/privcmd.c | 4 +-- fs/aio.c | 2 +- fs/autofs/dev-ioctl.c | 3 +- fs/autofs/root.c | 2 +- fs/binfmt_elf.c | 10 +++--- fs/btrfs/ioctl.c | 2 +- fs/compat_ioctl.c | 32 ++++++++++--------- fs/ext2/ioctl.c | 2 +- fs/ext4/ioctl.c | 2 +- fs/fat/file.c | 3 +- fs/fuse/file.c | 2 +- fs/namespace.c | 2 +- fs/readdir.c | 4 +-- fs/signalfd.c | 10 +++--- include/linux/mm.h | 2 +- include/linux/pagemap.h | 8 ++--- include/linux/socket.h | 2 +- include/linux/uaccess.h | 4 +++ ipc/shm.c | 4 +-- kernel/futex.c | 6 ++-- kernel/futex_compat.c | 2 +- kernel/power/user.c | 2 +- kernel/signal.c | 2 +- lib/iov_iter.c | 16 +++++----- lib/strncpy_from_user.c | 4 ++- lib/strnlen_user.c | 6 ++-- lib/test_kasan.c | 2 +- mm/gup.c | 4 +++ mm/memory.c | 2 +- mm/migrate.c | 4 +-- mm/process_vm_access.c | 13 ++++---- net/bluetooth/hidp/sock.c | 2 +- net/compat.c | 12 ++++--- sound/core/control_compat.c | 5 +-- sound/core/pcm_native.c | 5 +-- sound/core/timer_compat.c | 3 +- tools/testing/selftests/arm64/.gitignore | 1 + tools/testing/selftests/arm64/Makefile | 11 +++++++ .../testing/selftests/arm64/run_tags_test.sh | 12 +++++++ tools/testing/selftests/arm64/tags_test.c | 19 +++++++++++ 65 files changed, 232 insertions(+), 147 deletions(-) create mode 100644 tools/testing/selftests/arm64/.gitignore create mode 100644 tools/testing/selftests/arm64/Makefile create mode 100755 tools/testing/selftests/arm64/run_tags_test.sh create mode 100644 tools/testing/selftests/arm64/tags_test.c